1. Field of the Invention
This invention relates to a process of manufacturing a sintered body having at least one molybdenum-containing wear-resisting layer, wherein a low-alloy iron powder, which is intended to form the body of the member, and an iron-base metal powder, which contains non-alloyed molybdenum and is intended to form said wear-resisting layer are compacted to form a shaped member, which is subsequently sintered.
2. Description of the Prior Art
To provide valve tappets which can take up high loads for use in internal combustion engines, it is known (from German Patent Specification 2 822 902) to provide the valve tappet with a war-resisting sintered layer, which has a high molybdenum content of 20 to 35% by weight. That wear-resisting layer is formed in that a metal powder is compacted in a common mold together with the low-alloy iron powder used to form the body of the valve tappet. That metal powder consists of a carbon-free mixture of non-alloyed iron and non-alloyed molybdenum so that the valve tappet can be sintered at high sintering temperatures up to 1350.degree. C. by dry-phase sintering at a high sintering rate.
To increase the wear resistance the wear-resisting sintered layer is subsequently carburized so that mixed carbides are formed. Molybdenum is an excellent carbide-forming constituent and affords the additional advantage that the resulting layer has only a low tendency to corrode the material of the cam in contact with said layer. But said good material properties can be achieved only by an expensive manufacture because the sintering temperature must be relatively high and a carburizing is subsequently required.